1380cc as a daily driver?

Seems to me it's a matter of how you want to live with it. Here are some vague generalities others can split hairs about:

If you ask about longevity, this indicates you are into your mini for a greatly improved overall vehicle - not just the blast of raw power. Ask yourself what part of your mini you'd abuse to get what you want.

Extra stresses in the valve train, Pistons, rings, rods & crank, Transfer gears, tranny bearings, diff, ujoints - you get the picture. The contest is to ask what is reasonable throughout the whole progression, given optimized components that are given a chance to thrive -and survive.

Components you help to be more efficient can give you more power and their service life isn't compromised. Do your mini a favor and it'll repay you.

1380 with something less than a Kent 286 would be less stressed, and produce even more torque, probably. Maybe 276 and 1.3 roller rockers?

Higher compression multiplies heat, but is key to A series power. Find the middle course and remove all excess heat - that's fair.

Horsepower gives bragging rights and fast cruising, uphill & down. HP comes at higher rpms, which stresses engine components more.

Torque gives big pull and accelleration - brute force that comes at lower rpms, but is hard on drivelines, from the primary gear on out.

The greatest wear factor is your right foot and the next meanest is leaving it in a higher gear and relying on the torque.

Optimizing the entire unit means investing in stronger components and making their running lives easier, like balancing, keeping temps under control, setting up on a rollong road to eliminate overly lean or rich spots. Strong gearset and improved diff. Maintenance.

Big 13in wheels and meaty tyres stick too well. They allow the drivetrain no relief. Better to have less tread on the ground and a little slippage - it makes the car more fun to toss around anyway and it's easier to read the road and participate in the driving.

A sweet motor is a joy. Use it in moderation, letting it shout now and again, but with fresh oil, stout mountings, and good care. If you build it with the care a race motor gets, you could have a really pleasant, reliable ride.

........It's okay Alec, you can rest in peace now...........

David